In English, we call "muletillas" fillers or filler words. A filler word is a meaningless word, phrase, or sound that marks a pause or hesitation in speech. Common filler words in English are um, uh, er, ah, like, okay, right, and you know. (ie: I went to the store and...uh...like....she didn't buy anything). Some examples in Spanish are: este, pues, es que, viste, vale, etc.